This disclosure relates to a method of treating multiple sclerosis in a mammalian patient, preferably a human, in need of such treatment, comprising administering to said human an S1P receptor modulator or agonist, such as a compound of formula Ia or Ib, according to a dosing regimen that is determined with reference to the patient&rsquos blood lymphocyte count. An example of the compound of formula Ia or Ib is 1-{ 4-[1-(4-cyclohexyl-3-trifluoromethyl-benzyloxyimino)-ethyl]-2-ethyl-benzyl} -azetidine-3-carboxylic acid (siponimod).
